1. Field of Invention
This invention relates to a liquid detergent composition containing a liquid nonionic surfactant. More particularly, this invention relates to liquid detergent compositions, particularly non-aqueous liquid laundry detergent compositions which are stable against phase separation and gelation and are easily pourable and to the use of these compositions for cleaning soiled fabrics.
2. Discussion of Prior Art
Liquid laundry detergent compositions are well known in the art and in recent years have been actively and successfully commercialized. Because the liquid detergents are considered to be more convenient to use than dry powdered or particulate products, they have found substantial favor with consumers. They are readily measurable, speedily dissolved in the wash water, capable of being easily applied in concentrated solutions or dispersions to soiled areas and are non-dusting, and they usually occupy less storage space. Additionally, the liquid detergents may have incorporated in their formulations materials which could not stand drying operations without deterioration, which materials are often desirably employed in the manufacture of particulate detergent products. Although they are possessed of many advantages over unitary or particulate solid products, liquid detergents often have certain inherent disadvantages too, which have to be overcome to produce acceptable commercial detergent products. Thus, some such products separate out on storage and others separate out on cooling and are not readily redispersed. In some cases the product viscosity changes and it becomes either too thick to pour or so thin as to appear watery. Some clear products become cloudy and others gel on standing.
One particularly severe problem of the liquid laundry detergents based on liquid nonionic surfactants, especially non-aqueous formulations, is that the nonionics tend to gel when added to cold water. This is a particularly important problem in the ordinary use of European household automatic washing machines where the user places the laundry detergent composition in a dispensing unit (e.g. a dispensing drawer) of the machine. During the operation of the machine the detergent in the dispenser is subjected to a stream of cold water to transfer it to the main body of wash solution. Especially during the winter months when the detergent composition and water fed to the dispenser are particularly cold, the detergent viscosity increases markedly and a gel forms. As a result some of the composition is not flushed completely off the dispenser during operation of the machine, and a deposit of the composition builds up with repeated wash cycles, eventually requiring the user to flush the dispenser with hot water.
The gelling phenomenon can also be a problem whenever it is desired to carry out washing using cold water as may be recommended for certain synthetic and delicate fabrics or fabrics which can shrink in warm or hot water.
In addition to the gelling which may occur when the liquid nonionic detergent comes into contact with cold water gelling may also occur in the liquid detergent composition itself when the composition is transported or stored at low temperatures, such as in the winter months. Again, this is often a particularly severe problem in certain European countries where the common practice is to locate the clothes washer and cleaning supplies in unheated garages.
Partial solutions to the gelling problem have been proposed and include, for example, diluting the liquid nonionic detergent composition with certain viscosity controlling solvents and gel-inhibiting agents, such as lower alkanols, e.g. ethyl alcohol (see U.S. Pat. No. 3,953,380), alkali metal formates and adipates (see U.S. Pat. No. 4,368,147), hexylene glycol, polyethylene glycol, etc.
In U.S. Pat. No. 3,630,929-van Dijk, an acid substance is added to a substantially non-aqueous built liquid detergent composition containing a water-free liquid nonionic detergent surfactant, an inorganic carrier material and an inorganic or organic alkaline detergent builder to increase the rate of solution of the composition in water and to lower product viscosity. Suitable acid substances are disclosed as including inorganic acids, inorganic acid salts, organic acids, and anhydrides and organic acid salts. Among the organic acid salts, mention is made of succinic acid. Among the alkaline organic detergent builders mention is made of alkenyl succinates, e.g. sodium C.sub.12 alkenyl succinate, e.g. sodium C.sub.12 alkenyl succinate (anhydrous). All the data for dissolution rates and viscosities were obtained at 25.degree. C.
Attempts have also been made to reduce the gelling tendency of liquid nonionic detergent composition by modification and optimization of the structure of the nonionic detergent surfactant. As an example of nonionic surfactant modification one particularly successful result has been achieved by acidifying the hydroxyl moiety end group of the nonionic molecule. The advantages of introducing a carboxylic acid at the end of the nonionic include gel inhibition upon dilution; decreasing the nonionic pour point; and formation of an anionic surfactant when neutralized in the washing liquor. Nonionic structure optimization has centered on the chain length of the hydrophobic-lipophilic moiety and the number and make-up of alkylene oxide (e.g. ethylene oxide) units of the hydrophilic moiety. For example, it has been found that a C.sub.13 fatty alcohol ethoxylated with 8 moles of ethylene oxide presents only a limited tendency to gel formation. Certain mixed ethylene oxide-propylene oxide condensation products of fatty alcohols also exhibit a limited tendency to gel formation.
Nevertheless, still further improvements are desired in the gel inhibition of liquid detergent composition, especially non-aqueous liquid fabric treating detergent compositions.
Accordingly, it is an object of this invention to provide liquid nonionic surfactant-containing liquid detergent compositions which do not gel even when stored at cold temperatures for extended periods or when mixed with cold water.
It is another object of the invention to provide liquid fabric treating compositions which are suspensions of insoluble inorganic particles in a non-aqueous liquid and which are storage stable, easily pourable and dispersible in cold, warm or hot water.
Another object of this invention is to formulate highly built heavy duty non-aqueous liquid nonionic surfactant laundry detergent compositions which can be poured at all useful temperatures and which can be repeatedly dispersed from the dispensing unit of European style automatic laundry washing machines without fouling or plugging of the dispenser even during the winter months.
These and other objects of the invention which will become more apparent from the following detailed description of preferred embodiments are accomplished by adding to the liquid nonionic surfactant detergent composition a gel inhibiting compound in an amount effective to lower the gelling temperature of the nonionic surfactant compound by at least about 2.degree. C., the gel inhibiting compound being an aliphatic linear dicarboxylic acid having at least about 6 carbon atoms in the aliphatic portion of the molecule or an aliphatic monocyclic dicarboxylic acid wherein one of the carboxylic acid groups is bonded directly to a ring carbon atom and the other carboxylic acid group is bonded to the monocyclic ring through an alkyl or alkenyl chain having at least about 3 carbon atoms.
In one specific aspect the present invention provides a liquid heavy duty laundry composition composed of a suspension of a detergent builder salt in a liquid nonionic surfactant wherein the composition includes an amount of the dicarboxylic acid gel inhibiting to lower the temperature at which the composition will form a gel to no more than about 5.degree. C.
According to another specific aspect, the invention provides a method for dispensing a liquid nonionic laundry detergent composition into and/or with cold water without undergoing gelation. In particular, a method is provided for filling a container with a non-aqueous liquid laundry detergent composition in which the detergent is composed, at least predominantly, of a liquid nonionic surface active agent and for dispensing the composition from the container into an aqueous wash bath, wherein the dispensing is effected by directing a stream of unheated water onto the composition such that the composition is carried by the stream of water into the wash bath.